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Manure management could use a shift in perception

Nicole Kenney Rambo for Progressive Cattleman Published on 22 September 2017
Manure storage and handling

In light of volatility in commercial fertilizer prices, integrated crop and livestock operations are increasingly recognizing the value of manure as fertilizer.

Manure is a source of nitrogen (N), phosphorus (P) and potassium (K), and decreases commercial fertilizer needs. Further benefits of an integrated crop and livestock system include the addition of organic matter and sulfur (S) through fertilization with manure.

Co-products from ethanol and sweetener production are a source of moderate- to high-supply dietary S, resulting in an additional opportunity to improve crop yields through integrated feedlot and crop systems.

Manure is often thought of as a byproduct of beef production and consequently given minimal consideration. The level of consideration is generally correlated with the degree of oversight by state and federal regulatory agencies. The specific requirements vary by state and feedlot size but generally consist of the requirement for a manure or nutrient management plan.

Manure management plans broadly cover manure storage and handling, manure nutrient testing locations used for spreading, field-specific nutrient management and special considerations for management of sensitive areas.

Surely having a manure management plan and following applicable regulations should be the end of the discussion; however, I would encourage you to consider managing manure as a valuable resource. Retention of manure nutrients strongly depends on storage and handling methods.

Nutrient variability

A source of frustration in dealing with manure is the variability in manure nutrient concentrations. We rely on lab analysis to match manure nutrients with crop nutrient needs, but our ability to manage those manure nutrients is only as good as the sample we provide to the lab.

Are you collecting a representative sample to send to the lab? How many samples should you test to have an adequate understanding of the composition of manure produced by your operation?

Diet and bedding use will strongly influence manure nutrient concentrations. If you use certain pens predominantly for cattle on receiving and growing rations, and other pens for finishing cattle, you can improve the precision of your manure nutrient analysis by treating these areas as separate lots of manure.

The timing of the sample with respect to manure application is important. With exposure to the environment, manure nutrients will change.

Variability in manure nutrient concentrations are further compounded by inattention to precision during field application. Commercial fertilizer application is fine-tuned through applicator calibration – and even more so through variable-rate technology.

Variability in field application of manure can be reduced through manure spreader calibration. Further attention should be given to consistency of spread pattern. This is influenced both by manure spreader design but also consistency of routine maintenance.

Commercial fertilizer versus manure

A shift in perception of the comparative value of manure ultimately comes down to dollars and cents. Valuing manure relative to commercial fertilizer allows for accounting of the value of the cattle portion of diversified operations.

Similarly, the cattle-feeding portion of the operation should be charged the cost of farm-grown feed as well as cornstalks removed from the field for use as bedding. Evaluating profitability on both a farm and individual operational unit level can be very enlightening and useful in identifying areas for improvement.

The value of manure as fertilizer is a function of the concentration of N, P and K, and is relative to commercial fertilizer prices. Average manure composition generated in a 2014 University of Minnesota research project, funded by the Minnesota Corn Growers Association, on the impact of feedlot facility design on manure nutrient composition was used in calculating manure value.

The three facility types evaluated were open lots, bed packs and slatted floors over a deep pit configuration. Commercial fertilizer prices have been trending down through July 2017. Specific prices used are $500 per ton for anhydrous, $425 per ton for DAP and $339 per ton for potash.

Values are based on first-year availability of manure, assuming no incorporation of solid manure and sweep injection of liquid manure. Incorporation of manure is suggested as a best management practice; however, no incorporation is utilized in this example in order to generate conservative manure values. Availability of P and K are assumed at 80 and 90 percent, respectively.

Net manure value, gross value minus hauling costs, for solid manure is $3.58 and $5.07 per ton for bed pack and open lots, respectively. Value on a per-ton basis is lower for bed packs because manure nutrients are diluted by the addition of bedding, which generally has low nutrient density; however, greater tonnage of manure plus bedding is captured from bed packs, resulting in greater manure value per animal unit.

Yearly manure value per animal unit for bed packs is calculated at $17.90 compared to $15.21 for open lots. Net manure value for liquid manure from slatted floor over deep pits is $0.0096 per gallon or $24.12 per animal unit per year.

The magnitude of difference in value between feedlot facility types is driven by commercial fertilizer prices. When fertilizer prices are high, there will be a greater return on the value of manure from confinement facilities due to increased nutrient capture; however, when fertilizer prices are low, the value difference between facility types decreases due to increased hauling costs for bed packs and liquid manure on a per-unit basis relative to solid manure from open lots.

At the peak of fertilizer prices in 2013, the value of open lot, bed pack and liquid manure from slatted floor over deep pit were, on average, $43, $33 and $70 per headspace per year, respectively.

A greater emphasis on both the value of manure as a fertilizer and best management practices to minimize environmental overload of manure nutrients has resulted in greater consideration in manure-handling practices.

It is time to start thinking about manure as a co-product of beef production, rather than a byproduct, and proactively manage this resource with care.  end mark

PHOTO: Retention of manure nutrients strongly depends on the operation’s storage and handling methods. Producers are encouraged to create a manure management plan based on their state restrictions and guidelines. Staff photo.

Nicole Kenney
  • Nicole Kenney

  • Rambo
  • Feedlot Extension Educator
  • University of Minnesota
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